The present invention relates to the field of adjustable saw blades. More particularly, it relates to adjustable dado blades for cutting grooves or slots into wood.
Many devices are currently made for cutting grooves or slots, called dados, in wood. The devices fall into two general categories, wobble dados and stacking dados. The wobble dado generally contains a single blade mounted at an adjustable angle. The tilted blade cuts a channel into a piece of wood and appears to wobble as it spins. Some new wobble dados contain two blades in a V-shape. They are called V-wobble dados, and use the same principle as single blade wobble dados, but with two blades cutting instead of one.
Stacking dados generally contain two outer cutters, and a set of chippers to be mounted between the outer cutters. Depending on the width of the groove desired a different number of chippers are placed on the saw arbor between the outer blades. Adjustment of the wobble type of dado blade is fairly simple. Because of the tilt of the wobble blade, dados cut with wobble type dado blades are rounded at the bottom of the groove. Additionally, the cut quality is generally not very good. With stacking dados, the groove is normally flat at the bottom and the cut quality is high. However, the price paid for the flat, well cut grooves of stacking dado blades is difficulty in adjustment of groove width. The standard way to adjust groove width is by insertion of 1/8 inch or 1/16 inch chippers between the two main blades. Dado sets typically come with four to five chippers, one of which is 1/16 inch. This configuration allows for adjustment of groove width in 1/16 inch increments. In the past, fine adjustment of groove width has been made using metal, paper or plastic shims placed between one or more of the chippers and outer blades of the stacking dado. This adjustment procedure requires removal of at least the outer cutting blade and insertion of one or more shims to create a desired groove width. Saw set overlap maintains full width of cut between shimmed blades. The process is time consuming and inaccurate, often requiring multiple readjustments. More recently, some plastic shims have been marketed with a slot allowing the user to insert the shims on a saw arbor without removing the blades. However, these types of plastic shims do not work well because the spacing between saw blades is too small to properly insert and remove shims without removing the blades.
The objective of the present invention is to maintain the high quality cut of the stacking dado system, yet to allow the ease of adjustment of the wobble type dado system. The present invention provides a system capable of quick and easy fine adjustment of groove width without removal of the outer blade in a stacking dado system. Additionally, the present invention allows infinite adjustment of the groove width, limited only by the length of the saw arbor.
Other adjustable cutting blades exist in the prior art. For example, U.S. Pat. No. 2,788,812 (Jacobs) discloses an adjustable dado cutter having three blades. The blades move along their axis of rotation in response to rotation of an adjusting sleeve. However, Jacobs requires three blades, an arbor threaded with two different pitch threads that are opposite handed, and allow for proportional movement of the two movable saw blades in a 2:1 ratio. Jacobs does not disclose the simple construction of the present invention, nor does it allow for an infinite range of adjustment limited only to the length of the saw arbor. Additionally, the Jacobs device is not readily adaptable to existing dado cutting sets, nor does it allow for easy conversion from left hand to right hand arbor configurations. The present invention solves the problems encountered in the prior art, while simplifying the structure and performing more functions.